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Road Construction with PMB



Road Construction with PMB

Well done and expedient construction combined with crew safety and comfort are key ingredients to a successful paving job. When using Kraton technologies at your job, expect excellent mixture workability and compactability along with low fume emissions and odor.


Is paving with PmB any different?


The short answer is NO.

In general, asphalt mixtures made with PmB handle just like conventional mixtures under conventional paving temperatures and conditions. The difference may come when the mixtures cool off significantly and the polymer starts to reassemble itself, building cohesive strength (happens around 100°C or 212°F). The higher the polymer content the more pronounced the stiffening effect.

Keeping the mixture from cooling off is the simplest way of avoiding any issues. Proceed with compaction right behind the screed and you may actually find that the polymer modified asphalt mixtures compact very well and may help eliminate tender zone issues. This may be attributed to the shear thinning nature of liquid PmB – it keeps the mix more cohesive when no load is applied, but as soon as the compactor applies force the mix starts to rearrange.

Should I use the viscosity charts to determine the PmB mix compaction temperature?
No. The PmB materials are shear thinning. They do not follow the viscosity curves commonly used for non-modified asphalt. The Asphalt Institute has a great article on the topic.

How quickly could I open the PmB pavement to traffic?
Another benefit of using modified asphalt, and Highly Modified Asphalt in particular is the potential ability to open pavement to traffic much faster.

Can warm mix technology be used with polymer modified bitumen?
Warm mix asphalt technologies allow for 20-55°C reduction in asphalt mix production and placement temperature, enabling reduction in asphalt mixture fume emissions and lower fuel consumption during asphalt mixture production. Often these technologies carry an additional benefit of improving the asphalt mixture compactability.

Sometimes a question may arise regarding the compatibility of the warm mix technologies with SBS modified bitumen. The answer to this question is simple: Extensive field experience proves that SBS modified bitumen can be successfully used in conjunction with all three warm mix asphalt technology types:

· Foaming processes
· Wax (organic) additives
· Surfactant additives
 
What about occupational health and safety?

Porot et al. E&E 2020
The research indicates that, relative to unmodified bitumen, PmBs can achieve lower emission levels of volatile organic compound (VOC) and polycyclic aromatic hydrocarbons. (Porot et al)

 

References

Moseley, Howard.  “State of the Industry.”  Slide presentation at 2019 Florida Asphalt Conference.  

Porot et al, Laboratory evaluation of emissions from Polymer modified Bitumen, 7th E&E, Madrid, 2020

Life-cycle Assessment of 2012 NCAT Pavement Test Track Green Group Mixtures, NCAT Report 14-02, March 2014, National Center for Asphalt Technology, Willis R.J.

Mogawer W. et al., High-Performance Thin-Lift Overlays with High Reclaimed Asphalt Pavement Content and Warm-Mix Asphalt Technology: Performance and Workability Characteristics, Transportation Research Board, pp 18–28, 2012

Field results and practical experience with a new generation of SBS modified asphalt pavements, 6th Aus Road Eng, Melbourne Australia, 2011

Determining Lab Mixing and Compaction Temperatures for Binders, Asphalt Institute, 2016, website

 
 


 

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